The Boulton Paul Defiant was a British interceptor aircraft that served with the Royal Air Force (RAF) during the Second World War. The Defiant was designed and built byBoulton Paul Aircraft as a "turret fighter", without any forward-firing guns. It was a contemporary of the Royal Navy's Blackburn Roc. The concept of a turret fighter related directly to the successful First World War-era Bristol F.2 Fighter.
In combat, the Defiant was found to be reasonably effective at its intended task of destroying bombers, but vulnerable to the Luftwaffe's more agile, single-seat Messerschmitt Bf 109 fighters. The lack of forward armament proved to be a major weakness in daylight combat and its potential was only realized when it switched to night combat. It was supplanted in the night fighter role by the Bristol Beaufighter and de Havilland Mosquito. The Defiant found use in gunnery training, target towing, electronic countermeasuresand air-sea rescue. Among RAF pilots it had the nickname "Daffy".
Design and development
A pair of No. 264 Sqn.
Defiants. The Squadron Leader's aircraft "A" can be seen in the image at the top of the page.
The concept of a turret-armed defensive fighter emerged in 1935, at a time when the RAF anticipated having to defend Great Britain against massed formations of unescorted enemy bombers. Advances in aircraft design during the 1920s and 1930s had resulted in a generation of multi-engined bombers that were faster than the single-enginedbiplane fighters in service. The RAF believed that its turret-armed bombers, such as the Vickers Wellington, would be able to penetrate enemy airspace and defend themselves without fighter escort and also that the German Luftwaffe would be able to do the same.
In theory, turret-armed fighters would approach an enemy bomber from below or from the side and coordinate their fire. The separation of the tasks of flying the aircraft and firing the guns would allow the pilot to concentrate on putting the fighter into the best position while the gunner could engage the enemy. Previously the Hawker Demon had tested the concept with 59 of the biplane fighters (manufactured by Boulton Paul under a sub-contract) equipped with a powered rear turret, while the remainder of the series already manufactured were converted.
Air Ministry Specification F.9/35 required a two-seater day and night "turret fighter" capable of 290 mph at 15,000 ft. It followed the earlier F.5/33 which was for a pusher design with a front turret. F.5/33 had been abandoned as it offered little over existing fighters and the Armstrong Whitworth AW.34 design which had been ordered was not completed.
Boulton Paul, who had considerable experience with turrets from their earlier Overstrand bomber, submitted their P.82 design. Of the seven designs tendered, the P.82 was ranked second after Hawker's but ahead of Armstrong Whitworth's twin-engined design. The Air Ministry wanted several designs investigated and two prototypes of each. The Treasury agreed to seven prototypes (two Hawker, two Boulton Paul, two Fairey and one Armstrong Whitworth). Nonetheless, only prototypes of the P.82 and Hawker were built. Production orders were prepared for the Hawker but the Boulton Paul turret had the Air Ministry's attention. Delays by Hawker who were more focused on the Hurricane led to the P.82 receiving a production order in 1937 and the Hotspur order was cancelled in 1938.
The P.82 was a monocoque design constructed by bolting the sections together. This was the same as BP had used on other aircraft. The design had room for small bombs in recesses in the outer wing. Some of the development work from their B.1/35 tender carried over into the P.82.
The central feature of the P.82 was the four-gun turret based on a design by French aviation company SAMM, which had been licensed by Boulton Paul for use in the earlier Boulton Paul Sidestrand bomber but eventually installed in the "follow-up" design, the Boulton Paul Overstrand and Blackburn Roc naval fighter. The turret, 'Type A' was an electro-hydraulically powered "drop-in" unit with a crank-operated mechanical backup. The Defiant was armed with a powered dorsal turret, equipped with four 0.303 in (7.7 mm) Browning machine guns. The fuselage was fitted with aerodynamic fairings that helped mitigate the drag of the turret; they were pneumatically powered and could be lowered into the fuselage so that the turret could rotate freely. The Brownings were electrically fired and insulated cut-off points in the turret ring prevented the guns firing when they were pointing at the propeller disc or tailplane. The gunner could rotate the turret directly forward and transfer firing control of the guns to the pilot, with the guns firing along each side of the cockpit canopy. However, in practice this was rarely done as the turret's minimum forward elevation was 19° and the pilot did not have a gunsight.
An air-gunner of 264 Squadron wearing a GQ Parasuit
, or "rhino suit" (August 1940)
The gunner's hatch was in the rear of the turret, which had to be rotated to a side to enable entry and exit. There was not enough room in the turret for the gunner to wear a seat-type or back pack parachute so gunners were provided with a special all-in-one garment nicknamed the "rhino suit". To quote Frederick "Gus" Platts, air gunner in 230, 282 and 208 squadrons, "The Rhino suit we had to wear on Defiants was a bear but I couldn't come up with an alternative, even though it killed dozens of us. I forget the details of it but we could not have sat on our chute or even keep it nearby as in other turrets, so you wore – all in one – an inner layer that fitted a little like a wetsuit of today. The chute fitted around this, and then the dinghy and the outer clothing. There was inner webbing and pockets that literally fell apart (I presume) when one bailed out".
The first P.82 prototype (K8310) was rolled out in 1937 without its turret, looking like the Hawker Hurricane, although it was at least 1,500 lb (680 kg) heavier. A clean, simple and compactmonoplane structure had been achieved with main landing gear retracting into a broad mainplane section. The pilot's cockpit and rear turret were faired into a streamlined upper fuselage section. Fuel was carried in the wing centre section along with a large ventral radiator that completed the resemblance to the Hawker fighter. With a 1,030 hp (768 kW) Rolls-Royce Merlin I, the newly named Defiant prototype first flew on 11 August 1937, nearly a year ahead of the Hotspur. A second prototype, K8620 equipped with a turret was modified with telescopic radio masts, revision to the canopy and changes to the undercarriage fairing plates.
Completing its acceptance tests with the turret installed, the Defiant reached a top speed of 302 mph (486 km/h) and subsequently was declared the victor of the turret fighter competition. Apart from detail changes, the production Defiant Mk I looked similar to the two Defiant prototypes. As Boulton Paul were busy producing the Blackburn Roc naval turret fighter, the Defiant's service entry was delayed to such an extent that only three aircraft had reached the RAF by the start of the war. The Mk I was powered by the Rolls Royce Merlin III (1,030 hp/768 kW or 1,160 hp/865 kW)[N 1] with a total of 713 aircraft built.
The P.85 was Boulton Paul's tender to Specification O.30/35 for the naval turret fighter. A version of the Defiant for Fleet Air Arm (FAA); it had a deeper fuselage and leading edge slats for lower landing speeds required of carrier aircraft. The engine would be either a Bristol Hercules radial or the Merlin. Despite a higher estimated top speed, the Blackburn Roc was selected. With Blackburn already busy producing other projects, the detail design and production of the Roc was given to Boulton Paul. The only FAA use of the Defiant was as the target tug version.
The first Defiant prototype had not been initially fitted with a turret and therefore had an impressive top speed. In 1940, Boulton Paul removed the turret from the prototype as a demonstrator for a fixed-gun fighter based on Defiant components. The armament offered was either 12 .303 in (7.7 mm) Browning machine guns (six per wing) or four 20 mm Hispano replacing eight of the Brownings. The guns could be depressed for ground attack. By that time, the RAF had sufficient quantities of Hawker Hurricanes and Supermarine Spitfire and did not require a new single-seat fighter. With a calculated top speed of about 360 mph (579 km/h) at 21,700 ft, the P.94 was almost as fast as a contemporary Spitfire although less manoeuvrable.
In October 1939, No. 264 (Madras Presidency) Squadron was reformed at RAF Sutton Bridge to operate the Defiant. Initial training and development of tactics began with other aircraft as it received its first Defiants only in early December at Martlesham Heath. They began night fighter training in February 1940. The squadron tested its tactics against British medium bombers – Hampdens and Blenheims – and 264's CO flew against Robert Stanford Tuck in a Spitfire, showing that the Defiant could defend itself by circling and keeping its speed up. By March, 264 Squadron had two flights operational with Defiants and No. 141 Squadron received its first Defiant. When the Defiant was first introduced to the public, the RAF put out a disinformation campaign, stating that the Defiant had 21 guns: four in the turret, fourteen in the wings and three cannon in the nose.
The first operational sortie came on 12 May 1940. Defiants flew with six Spitfires of 66 Sqn, and a Ju 88 was shot down over the Netherlands. The following day, in a patrol that was a repetition of the first, Defiants claimed four Ju 87s, but were subsequently attacked by Bf 109Es. The escorting Spitfires were unable to prevent five of the six Defiants being shot down by a frontal attack.
During the evacuation of the British Expeditionary Force from Dunkirk, the squadron was forward-based at RAF Manston, as one of the 16 squadrons that No. 11 Group had available to cover the evacuation. On the 27th, 264 Sqn claimed three He 111 and two damaged. On the 28th, shortly after takeoff, ten Defiants were attacked by about 30 Bf 109s – forming a circle, they claimed six German fighters for the loss of three Defiants.
The Defiant was initially successful against enemy aircraft. Its best day was 29 May 1940, when No. 264 Sqn claimed 37 kills in two sorties: 19 Junkers Ju 87 Stuka dive bombers, mostly picked off as they came out of their dives, nine Messerschmitt Bf 110 twin-engined heavy fighters, eight Bf 109s, and a Ju-88. One Defiant gunner was lost after he bailed out, although the aircraft made it back to its base to be repaired.
E R Thorn (pilot, left) and F J Barker (air gunner) pose with their Defiant after destroying their 13th Axis aircraft; Thorn and Barker were the most successful Defiant crew of the war.